Manufacture of metallic tubing



N05. 1 6, 1937. R TQNDEUR 2,099,040

MANUFACTURE OF METALLIC TUBING Filed July 26, 1935 Fig. I.

AAAAAAAAA l l Patented Nov. 16, 1937 UNITED STATES PATENT OFFEQE MANUFACTURE OF METALLIC TUBING Rene Tondeur, London, England Application July 26, 1935, Serial No. 33,287 In Great Britain July 30, 1934 8 Claims.

: 10 termed .Bowden mechanism.

As described in my previous specification aforesaid, flexible tubing, designed to form the outer member of such Bowden mechanism is composed of two for'more closely interwound open-coiled wires having such a pitch and cross-sectional shape, that the coils are at all times in normal use in continuous spiral contacting relationship, .so as to render the interwound coil tubing selfsustaining against relative bodily lateral displacementof the coils under axial compression, Whilst the interwound coils are adapted, when flexed, to mutually interact to cause relative transverse movements of the curved portions of the respective coils to be set up between them, so that they :25 move into and out of concentric relationship withrout 's'ubstantiailly'varyiiig the elfective axial length I :of the tubing :as a whole.

Such tubing composed of two closely interwound open coils can comprise one coil formed of .round section and the other of trapezoidal or like section, or one coil formed of trapezoidal or like section and the other of reverse trapezoidal .or like section. It can also contain four for more even number'tof coils of appropriate section, though this in general gives little advantage and there Jis'a :danger, if the number of coils be increased, a

" that theipitch of each coil becomes so coarse that .bird -caging under axial load may result.

Where in the following description in connection with Bowden mechanized tubings I speak of the leading coil and following coils it is to be understood that the leading coil maybe formed of triangular or trapezoidal wire wound base inward, .inwhich 'case the following coil whose wind- 45 in'gs are forced between those of the former, is

formed either of wire-of triangular or trapezoidal section wound base outward or wire of round section, or the leading coil may be formed of wire of round section in which case the following coil is formed-of wire of triangular or trapezoidal section wound base outward.

Coiled tubings such as are hereinabove referred to are better able to withstand axial compression or tensional forces the greater the tensile strength 7 of the wire used in their construction. Wires of high tensile strength capable of being coiled, e. g., music wire, are, however, expensive compared with wire of lower tensilestrength, and an aim of the present invention is to increase the strength of the tubing without resorting to such expensive wires.

.It would be possible to heat treat and harden the tubing after completion, but the tensioning of the tubing set up by the winding and interwinding or coiling and intercoiling of the wires 10 composing it would be destroyed or diminished by such treatment, and the desired resistance to compressive forces would not be attained.

According to the main feature of the present invention the leading wire is wound or coiled in a comparatively soft condition, which permits of the operation being easily eifected, and when in coiled shape is heat treated and hardened to the desired'degree of hardness after which the turns of the following coil are forced between those of the leading coil by winding or coiling. Preferably the process is carried out in continuous fashion so that a suitable length of the leading coil is formed and is heat treated and hardened to the desired degree of hardness before arriving at the station at which the following wire is introduced between its windings. In this way the forming of the leading coil, its heat treatment and hardening, and the winding and. coiling of the following coil proceeds simultaneously, there being always a predetermined length of the leading wire in the hardening zone prior to its reaching the station at which the following wire is introduced.

The invention has the advantage of enabling Wires to be used in the production of such tubing which afford great resistance to axial compressive forces, and also enable the tubing the better to resist axial tensional forces, and lends itself to economy of material. Further or alternatively it allows cheaper wire to be used to form a tubing having properties which formerly could only be obtained by the use of more expensive material.

This process enables us to use a leading wire of low tensile strength, e. g., 60 tons tensile strength,

which can be greatly increased, e. g., up to 160 tons tensile strength, by the hardening treatment after coiling, so that a tubing composed of one relatively cheap wire and another wire of say 100 tons tensile strength can be produced which will withstand. the same axial forces as two more expensive wires, or alternatively, a tubing can be produced which will withstand greater axial forces than known tubings without increase in cost.

Two ways of carrying out the present invention .55

35 frequency induction furnace 4 as shown in Fig. 2.

are illustrated diagrammatically by Figs. 1 and 2 in the accompanying drawing, Fig. 3 showing by way of example a piece of two wire tubing which can be produced by the present method.

In Fig. 1 the coil l passes through an electrical heat treament apparatus comprising spaced. pairs of contact rollers or like 2 which may be Water cooled copper rollers which are in an open circuit 3 which is closed by that part of the coil I which for the time being bridges the gap between the contact rollers 2, the strength'of the current being so, chosen with respect to the rate. of feed of the coil andthedistance the contacts are spaced apart, that the coilis heated -t"o5900 C. or thereabouts and is hardenedby air blast or other cooling or quenching previously to the introduction of the following wire or wires.

The open circuit 3 may have therein a vari-" able resistance, a single pole switch, an ammeter and the secondary winding of a transformer, the

' the contacts of- 10 inches, thespeed of the coil going through being five feet a minute.

An alternative method of heating the coil would be to cause it to advancethrough ahigh In both Figs. 1 and 2, 5 and 6- indicate the leading and following wires respectively which are led from spools I and 8 to coiling machines flexibility of the shaft and its outer casing or 9 and 10 respectively, these coiling machines being so interconnected that the correct amount of wire is coiled in each, and the following wires being by way of example steel wire of 100 tons tensile strength, i. e., having a degree of hardness suited for winding or coiling without having its temper reduced. r.

In this way the material chosen for the leading wire 5 may be steel of a particularly high tensile value for instance, the spring steel which is customarily used for exhaust valve springs, as I coil or wind theleading wire while such steel is in a soft or low tempered condition and then heat treat and harden the steel to the desired degree of hardness after winding or coiling, an operation for which such steel insuch hardened condition would not be suited. 1

Not only am I thus able to produce a coil capable of withstanding greater tensional axial forces but I secure the choice of using sections larger or more of ribbonlike character in the radial direction of the coil than would be practical in. the case of winding or coiling hard wire of high tensile strength.

If the winding of the coils is carried out with ening of the first coil to take place it will usually be necessary to employa special mandrel having a medial coupling section with which the coiled leading wire does not make contact .in passing through the electric or other heating zone, and arrange the respective chucks, which grip the rotating mandrels which serve for winding the wires therearound after they have been led through dies of the kind described in my previous application aforesaid, to be spring urged towards each other so that the winding is effected against such spring pressure.

In this mode of working it will usually be necessary to protect the mandrel from undue heating.

To compensatefor any inequality of the elastic strength of the heat treated and hardened leading wire and the following wire, or wires,

wire for the latter may be chosen which is of appropriately larger sectional area than the leading wire.

' One of the advantages of the present invention is that it"enables the margin of allowance for permanent reduction of a given length of the tubing under compressive load to be reduced and thereby to conduce to more economic use of. material and greater accuracy and reliability in assembled and adjusted mechanisms.

Instead of winding both wires, I may'wind the first wire and coilthe. second, in which case 1 the necessity of usinga special mandrel is avoid-- ed, or otherwise, I may arrange to coil both wire as hereinbefore stated. g Tubing according to the present invention is .also applicable to various uses for which a fluid tight conduit serves,.for example, for conveying or retaining fluids particularly liquids such as lubricants under pressure, or for conducting wires,.rods, air under pressure, etc., or for use as the outer casing or covering of flexible shafting, such as is used for transferring motion from a source of power usually to some kind-of tool or. abrasive wheel which isrequired to be permitted tobe moved in any direction by the covering, the latter forming a bearing for the core of the flexible shafting and also astationary covering which enables the shaft as awhole 1 .to be handled readily while the inner member is revolving.

What I claim is:-- 1. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding a leading wire while this is in a soft condition, then heat-treating and hardening the wire to the desired degree of hard! ness, and then introducing between the windings of the leading wire or wires an already tempered following wire or wires.

2. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding a leading wire while this is in a soft condition, and whilst the coiling or winding proceeds heat-treating and hardening the wire to the desired degree of hardness, and then introducing between the windings of the leading wire or wires an already tempered following wire or wires. r

. 3. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding one or more leading wires whilst in a soft condition, and whilst the winding or coiling, winding or coiling one or more already tempered following wires between the windings of the hardened leading wire.

4. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding a leading wire while" this is in a soft condition, applying an electric current to a length of the coiled wire so as to heat said wire incidental to hardening it and introducing between the windings of the hardened wire an already tempered following wire or wires.

5. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding a leading wire while this is in a soft condition, then advancing the coiled wire through a high frequency induction furnace so as to heat said wire incidental to hardening it, and then introducing between the windings of the hardened wire an already tempered following wire.

6. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding one or more leading wires whilst in a soft condition, and whilst the coiling or winding proceeds applying an electric current to a length of the coiled wire so as to heat said wire incidental to hardening it, and simultaneously with the aforesaid winding or coiling operation, winding or coiling one or more already tempered following wires between the winding of the hardened leading wire.

7. Process as in claim 3, wherein the coiled soft wire is passed through a high frequency induction furnace.

8. Process for the production of flexible tubing composed of multiple interwound coils, which consists in coiling or winding at least one relatively soft wire, then heat-treating and hardening said wire to the desired degree of hardness, and then forcing between the windings of the sohardened wire at least one already tempered following wire.

RENE TONDEUR. 

